Method and apparatus for storing surplus ADSS cable

ABSTRACT

A method of storing surplus ADSS cable includes steps of laying out a length of cable along an aerial route defined by a series of poles and forming loops of surplus cable at occasional poles. The cable is raised to a predetermined installation height at each pole. Two dead-ends at the pole secure the ends of the loop so that the loop is substantially free of tension. The center of the loop is raised and secured to the pole while maintaining the minimum bend radius, thus forming two bights in the loop. A bend radius protector is installed in each of the bights to protect the cable. Each bend radius protector is suspended from a cable protecting sleeve placed over the taut cable, so that the cable is not damaged. An apparatus for practicing the method is also disclosed.

BACKGROUND OF THE INVENTION

This invention relates to the art of data transmission and moreparticularly to a method and apparatus for storing surplus ADSS cablealong an aerial route. ADSS is an acronym for "all-dielectricself-supporting". Such cable has a strong non-metallic sheath whichsupports the optical fibers making up the cable. ADSS cable may alsohave a reinforcing strand at its core. All-dielectric cable has theadvantage that it can be used in close proximity to electrical powerlines, whereas conventional communications cable are required to be runin a separate zone, usually at least forty inches below the powercables.

Optical cable is vulnerable to damage (fiber breakage) from bending andtwisting, and performs best when sag and twisting are minimized. Cablemanufacturers specify a minimum bend radius which must be strictlyobserved to avoid fiber damage. Currently, as a rule of thumb, the bendradius cannot be less than ten times the cable diameter for anunstressed cable, fifteen times the diameter for a stressed cable. Thisrule of thumb may change as cable construction changes; the trendappears to be toward cables having smaller minimum bend radii. In anyevent, devices used to store surplus cable, must protect the cable frombending too sharply, that is, at less than the specified minimum bendradius.

Fiber optic cable is typically installed on aerial routes in very longlengths so as to minimize the number of splices, each of which degradesoptical signals. To allow for rerouting, such as pole movement, and forrepairs, it is important to provide slack in the form of surplus lengthsof cable at intervals along the route, so that entire long lengths ofcable do not have to be taken down when minor repair or rerouting isrequired. The more frequent the storage interval, the less the probablelength of cable which must be rehung if rerouting is necessary. Thesurplus cable may be stored either below ground, or along the aerialroute.

In the underground storage method, the cable is routed from its aerialattachment location down a pole and into an underground enclosure. Thecable is coiled within the enclosure, and then routed back up the poleto continue along the main cable route. This method is presently thepredominantly accepted method for storing surplus ADSS cable, but it ishas several disadvantages.

First, underground storage requires an expensive, watertight,underground enclosure and necessitates the expense of excavation.Moreover, an unobstructed excavation site is not always available at theexact pole location where the cable must be stored.

Second, an enclosure sometimes does not provide sufficient space tostore the required length of cable in a manner that renders the cableeasy to access and manage when access is necessary. If the pole has tobe relocated subsequently, there is an additional moving expense ofexcavation at the new pole site to install the container.

Third, the fact that the cable must be routed up and down the pole fromthe aerial attachment location to the underground enclosure makes thecable vulnerable to damage from collisions (e.g., auto accidents, beingstruck by mowers, etc.) and from vandalism. Any such damage to ADSScable would require potentially extensive and costly cable replacementattended by unacceptable loss of service. Clearly, an aerial method ofstoring ADSS cable would avoid the drawbacks of the underground storagemethod just described.

For aerial storage, it has been proposed to run surplus optical cablearound snowshoe or teardrop shaped devices to avoid overbending. PriorU.S. Pat. No. 5,092,663 (Hivner) and 5,408,517 (Kaplan) exemplify priordevices. These devices, however, were designed for pre-ADSS fiber opticcable, which does not have sufficient strength to support itself, andmust be lashed to or otherwise supported from a steel or metallicmessenger cable. While prior inventions are acceptable for storingmessenger-supported fiber optic cable, no provision has been offeredwhich would make such inventions suitable for use with ADSS cable, whichmust be protected at all times not only from overbending, but also fromincidental contact and abrasion.

In the installation of messenger-supported fiber optic cable,attachments of any necessary hardware such as that described in thepatents mentioned above may be made directly to the steel messengercable without any danger of damaging the fiber optic cable. In the caseof ADSS cable, however, the supporting member is the outer sheath of thecable, which is subject to possible damage if any attachment which isnot properly designed is made directly to the cable.

A problem related to that of surplus cable storage is that of supportingsplices between cables. Splicing is usually done at ground level in atruck or trailer containing special splicing apparatus. Therefore,enough excess cable must be provided at the splice so that it can reachthe ground. Additionally, once the splice has been made, it is securedin a box known as a "splice closure", which may weigh as much as 35pounds. Because of their weight, such closures have been mounted on thepole in the past, but this creates a confusion of cables near the pole,where they might be damaged, and without any guarantee of minimum bendradius protection. It would be better to support the splice box from thecable, if one could avoid injuring the cable.

SUMMARY OF THE INVENTION

An object of the invention is to provide an above-ground method ofstoring surplus ADSS cable along an aerial route.

Another object of the invention is to permit such a method to bepracticed at any height above the ground, so as to avoid other utilityattachments. A related object is to enable communications cables to beinstalled in the power zone on a utility pole.

A further object of the invention is to protect fiber optic cable fromdamage by being struck by automobiles, mowing equipment and the like.

Yet another object is to facilitate access to stored cable whennecessary.

An additional object of the invention is to provide a method andapparatus for storing a sufficient length of surplus ADSS cable so thatthe cable may be conveniently and safely relocated to a vehicle atground level for splicing operations, and then conveniently restored tothe aerial storage location once splicing is completed. A related objectis to facilitate relocating a pole supporting the cable, when necessary.

Another object of the invention is to provide means for storing ADSScable which does not itself endanger the integrity of the cable.

Yet another object is to permit the storage of an unlimited length ofsurplus ADSS cable.

One further object is to provide a method and apparatus for storingsurplus ADSS cable in a manner which is economical of materials andlabor.

One other object of the invention is to provide a way of installing asplice closure at a surplus loop installation location.

These and other objects are attained by an apparatus for storing asurplus length of ADSS cable on a pole. The apparatus includes a pair ofdead ends, each connecting to the pole, for relieving line tension sothat the surplus length is not under tension, a pair of snowshoe-shapedbend radius protectors for supporting opposed ends of a loop of surpluscable, on the main part of the cable which is under tension, apole-mounted multiple cable guide for supporting the ends and the middleof the loop and to protect the cable as it passes the pole, and a pairof cable protection sleeves, one attached to each of the radiusprotectors, for suspending the protectors from the main line undertension. In one embodiment of the invention, cable splice closures areaerially supported as well.

The invention also provides methods of storing and splicing opticalcable, using the inventive apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIG. 1 is a perspective view of an aerial installation of optical cablesupported by a series of poles;

FIG. 2 is an enlarged view corresponding to a portion of FIG. 1, showinga single pole and a surplus loop of ADSS cable laid out adjacent thepole;

FIG. 3 is a view like FIG. 2, showing the center of the loop raised tothe level of the cable;

FIG. 4 is a view like FIG. 3, showing one bight of the loop supportedaccording to the invention;

FIG. 5 shows the loop at the end of installation;

FIG. 6 is an exploded detail view of a cable guide attached to a pole,between two dead-ends;

FIG. 7 is an exploded view of an aluminum bend radius protectorsuspended from a metallic cable protecting sleeve;

FIG. 8 is an exploded view of an alternate, non-conductive bend radiusprotector, suspended from a non-metallic cable protecting sleeve;

FIG. 9 is an exploded view of an inline splice closure box hung from oneof the dead-ends;

FIG. 10 shows a butt splice installation; and

FIG. 11 shows details of hardware for suspending a splice closure from adead-end.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An all-dielectric self-supporting optical cable installation is shown inFIG. 1. A series of poles P inserted in the ground at possibly unevenintervals define an aerial route. An ADSS optical cable thousands offeet long is installed at a specified installation height above theground along the poles, and surplus lengths of cable are laid out atsome of the poles (about four or five loops per mile). Each loop mayhave a length of a hundred feet, more or less, to allow for polerelocations and to provide enough cable to reach a splicing truck, ifnecessary. The poles other than those at which the loops are laid outhave conventional cable-supporting hardware.

One of the loop-supporting poles is shown in greater detail in FIG. 2.Here, the taut cable 10 extends in either direction from the pole, andis maintained under tension by two dead-ends 12, 14 which grasp thecable and transfer its tension to the pole, so that the loop 16 ofsurplus cable is substantially tension-free. Markers are laid out aroundthe loop to protect it from accidental damage.

A dead-end (FIG. 5) is a piece of hardware which grips the cable passingthrough it like a Chinese finger trap. It comprises two or more layersof wires 18 wrapped around the cable in helical fashion; alternatinglayers have opposite hand. The proximal end of the wires are formed intoa loop 20 which is attached to the clevis at one end of a rigid link 22,the other end of which is secured to the pole.

In FIG. 2, the base 23 of a cable guide, having three channels 24, 26,28, has been attached to the pole by two lag screws 30. See FIG. 6 for adetail.

In FIG. 3, a worker has laid the two ends of the loop in the upper twochannels of the guide base, and has raised the center of the loop fromthe ground, placing it in the bottom channel, while taking care not tobend the cable beyond its minimum bend radius. The guide cap 32 (FIG. 6)has been placed over the cables, and lag screws 34 are driven throughholes in both blocks, into the pole. The free ends of the loop now formbights "B" which hang down from the pole.

Next, the bights are raised (one at a time) and bound to the taut cableby hardware such as bands 36 (FIG. 4), working outward from the pole.Taking care to maintain bend radius above the minimum, the worker lastlyinstalls a bend radius protector 40 at the ends of each bight, andsuspends the protector from the taught cable, clamping over a cableprotecting sleeve 50 (FIG. 5) which he has placed on the cable. Thesleeve (see FIG. 7) comprises, like the dead-ends, an array of wireswhich wind helically around the cable, protecting it from abrasion andcrimping damage.

Alternatively, the sleeve may be formed (FIG. 8) of two plastichalf-shells 52,54 bolted together around the cable. The tabs 56 shownreceive clamping bolts, and two of the outermost provide means forsuspending the bend radius protector. A hard foam bushing 58 is placedbetween the shells and the cable, lightly clamping it, to prevent theradius protector from swaying. Bushings of different inside diametersmay be provided to accommodate cables of different size.

If the protecting sleeve of FIG. 7 is used, the bend radius protector issuspended from it by means of a two clamps, each comprising two halves60,62 which are bolted together around the protecting sleeve; the clampsare in turn secured to the cross-braces by means of stud plates andnuts, as shown in FIG. 7.

The bend radius protector 40 is a metallic (FIG. 7) or plastic (FIG. 8)device having the shape of a snowshoe. The periphery of the device isformed by a channel member 42 arranged groove outward (alternatively,the groove could face perpendicular to the plane of the device). Thegroove preferably is half-round, of a radius like that of the largestcontemplated cable. The channel is reinforced by front and rearcross-braces 44,46 which also provide means for suspending theprotector. In the metallic version (FIG. 7), the cross braces have apair of holes for receiving studs on a stud plate 48 which is installedfrom the bottom so that the studs protrude through the holes, and theclamps can be installed over them. In the plastic version (FIG. 8),pairs of tabs 49 are molded onto the upper surfaces of the crossbraces,and the appropriate tabs of the two-piece protecting sleeve areinstalled between the tabs, and secured by through-bolts.

While metallic bend radius protectors have the advantage of being easyto manufacture, it is expected that bend radius protectors made entirelyof plastic will become preferred for reasons of cost and safety. Whichplastic material may be selected eventually is not now known. Wecontemplate that a strong structural foam, possibly a skinned foam, maybe most preferred.

Utility poles commonly carry power lines in a power transmission zone atthe top of the poles, and telephone lines in a communications zone belowthe power transmission zone. A radius protector made of metal may beappropriate in the communications zone (lower on the pole); however, aplastic unit should be used if the cable is run in the powertransmission zone, for worker safety and to avoid other problems ofinduced voltage.

Directions for installing a cable according to this invention follow.

Initially, evaluate of the route must be performed to establish at whichlocations (i.e., poles) the surplus cable should be installed. All suchpole locations, along with the corresponding surplus loop lengths,should be indicated on the final project plans furnished to theinstallation crew. Each pole where a surplus cable loop is to beinstalled should be marked to identify the location of a surplus looppoint prior to, or ahead of, the installation of the main cable route bythe installation crew.

At the first surplus loop location, dead-end the ADSS cable usingapproved dead-end hardware at the proper attachment height on the pole.

After the first dead-end is properly secured, remove the predeterminedlength of surplus ADSS cable from the spool. Lay out one fourth of thetotal surplus cable length ahead in the direction of the main cable run,then loop back toward the dead-end pole. Continue to lay out cable pastthe pole to a point one fourth of the total surplus loop length in theopposite direction, then loop back and return the dead-end pole.

Raise the end of the total length of the surplus cable loop to theproper attachment height and dead-end the cable in the oppositedirection from the first dead-end attachment.

The entire length of the surplus loop is now independent of the maincable run and should be laid out directly under the main, overhead cablewith one-half of the surplus loop ahead of the pole and the remainingone-half of the loop rearward. Place the appropriate protection andcaution markers at the location of the surplus loop to prevent damage tothe cable.

Continue to install the main ADSS cable route along the pole line to thenext surplus cable pole location and repeat the dead-end and layoutprocedure described above.

At the proper attachment height, install one half of the cable guide tothe pole, using two lag screws inserted through the countersunk holes atthe center of the unit. Drive the lag screws into the pole so that theheads are flush with the mating surface of the unit, but do notover-tighten.

To install a surplus loop on the pole, locate the mid-point of the loopand raise it to the multiple cable guide. Position the beginning sectionof the cable loop into the top cable channel, the ending section intothe middle cable channel, and the mid section of the loop into thebottom channel.

With all three cable sections properly positioned, install the secondhalf of the multiple cable guide over the cables and secure it using thetwo remaining lag screws. Apply only enough torque to draw the twohalves of the unit together. Use caution not to bind any portion of thecable between the two halves of the multiple cable guide duringinstallation.

After the mid-portion of the loop is properly secured to the pole, beginraising short sections of the forward or rearward half of the loop tothe main cable run and secure the two loop sections to the main cableusing mid-span cable clamps or tie wraps. Continue to raise and attachthe cable loop until the end of the loop half is reached, leaving enoughof the loop end free so that it can be installed onto a bend radiusprotector.

Now, install one cable protection sleeve onto the maid cable at thelocation of the first bend radius protector. The cable protection sleeveis installed by wrapping the spiral rod sections around the cable untilthe entire section of cable is enclosed in the complete cable protectionsleeve. Using the end of the cable loop section as a guide, make surethat the cable protection sleeve is positioned on the cable in a mannerthat will allow the sleeve clamps or bend radius protector mounting tabs(which will support the bend radius protector) to attach directly to thecable protection sleeve.

Install the end loop of the surplus cable into the channel of the bendradius protector to attach directly to the cable protection sleeve.

Install the end loop of the surplus cable into the channel of the bendradius protector and secure it at the proper locations around thechannel using cable ties.

Slide the two halves of each sleeve clamp assembly apart and positionthe front and rear clamp assemblies around the armor rod. Next, slidethe two clamp halves of each clamp armor rod. Next, slide the two clamphalves of each clamp assembly together and tighten the nuts located onthe stud plates. Install a bolt through the top hole of each clamp andsecure the clamps using nuts. Avoid using excessive force, which maydistort the armor rod assembly and possibly damage the cable.

Repeat the preceding four steps to install the remaining half of thesurplus loop, armor rod assembly, and bend radius protector.

FIGS. 9 and 10 show splice closures supported from an aerial cableaccording to the invention. In FIG. 9, two cables are joined end-to-endin an inline splice. In FIG. 10, a butt splice has been formed betweentwo cables whose ends pass in the same direction into a closure.

In FIG. 9, an inline splice closure 70 has been added to the arrangementshown in FIG. 5. The closure contains an end-to-end cable splice formedat ground level and secured in the closure, which has been subsequentlysuspended from the dead-end 12 by clamps like those shown in FIG. 7.

FIG. 11 shows the clamps in greater detail. Each clamp has two parts60,62 that are bolted together around the dead-end 12. Note that eachstud plate has been modified by welding a horizontal rod 72 to one side.The stud plates 48' are installed with their respective rods facing awayfrom one another so as to simulate a cable messenger. Now, standardsuspension hardware 74 provided by the closure manufacturer, intendedfor messenger-type cables, can be hung from the simulated "messenger".This suspension arrangement is suitable for butt-splice closures aswell.

In FIG. 10, a butt-type splice has been formed, and the splice closure70' is about to be hung from the dead-end 14, by means of clamps similarto those shown in FIG. 7. If it is not possible to locate the closurebeneath the dead-end, a cable protection sleeve may be placed around thecable beyond the dead-end, and the closure then is hung from the sleeve.Either way, the cable routing is more complex, and a second multiplecable guide and a third bend radius protector are required. The secondguide 18' is installed just below the original guide, and the third bendradius protector 40' is suspended from the dead-end on the opposite sideof the pole. The routing of the surplus cable is as follows: from theleft dead-end, through the middle channel of the cable guide, around theright bend radius protector, back through the top channel of the secondcable guide to the third bend radius protector, then back through themiddle channel of the second cable guide to the splice closure. Thesucceeding cable emerges from the splice closure, passes through thebottom channel of the top cable guide, around the left bend radiusprotector, and back through the top channel of the top cable guide tothe right dead-end. Obviously, which channels are used is not critical,but the routing specified avoids confusion. One might, of course, use asingle cable guide with five or more channels instead of the twodescribed.

If a cable splice is required during installation of a surplus loop, thefollowing procedure should be followed:

The splice (either an in-line splice or a butt splice) should be locatedso at a point along the surplus loop that will allow the splice closureto be installed onto the smallest wire wrap of one dead-end assembly(approximately five to six feet from the mid-point of the surplus loop).

If the splice is to be made relative to a cable reel end, make sure thatthere is a sufficient length of cable on the end of the reel at the polelocation to make a complete forward one-half loop of surplus cablebeyond the pole and that the return end of the cable will fall withinfive to six feet of the pole.

With the main cable dead-ended in both direction, the splice closurecomplete, and the surplus loop laid out properly, raise the spliceclosure to the proper dead-end and attach the splice closure to thesmallest wire wrap of the dead-end assembly using two splice closureinstallation clamp assemblies.

A butt splice may also be located along the surplus loop length of cableeither at the end of a cable reel, or at any point along the cableinstallation. An additional bend radius protector and one additionalpole guide assembly is required for a butt-type splice. FIG. 10 showsthe proper cable routing.

Repeat the previously described procedure, raising and supporting theremaining half of the surplus loop in the opposite direction.

Install one cable protection sleeve around the main cable at eachlocation where a bend radius protector is to be installed. Using theunsupported end of the loop as a guide, locate the cable protectionsleeve so that each end of the sleeve will align as closely as possiblewith each end of the bend radius protector when the bracket is in itsfinal installed position. This will allow for any minor adjustments inthe location of the radius protector which may have to be made to removeslack from surplus cable.

Fit two hanger brackets to each bend radius protector, if supportbrackets are not pre-formed on the bend radius protector.

Place the unsupported loop end of one section of surplus cable into thesnowshoe channel and secure the cable in the channel with tie-straps.

An in-line splice closure may be located along the surplus loop of cableeither at the end of a cable reel, or at any point along the cableinstallation.

To install a surplus loop and a splice closure where the surplus loopdoes not represent the end of the reel cable: First, with the main runof cable properly dead-ended in both directions and the surplus loopready for installation to its aerial location, identify a point on thesurplus loop approximately five to six feet from the mid-point of thesurplus loop in either direction from the pole. Make the required spliceat this point and install the appropriate splice closure onto the cable.Next, raise the splice closure to the attachment height of the dead-endclosest to the splice point and attach the splice closure directly tothe smallest diameter wire wrap of the dead-end assembly using spliceclosure installation brackets. After the splice closure is properlysecured to the dead-end, install the multiple cable guide and secure thethree sections roof the surplus loop as described above. Continue withthe surplus loop installation procedure described above until the entiresurplus loop is properly adjusted and secure.

To install a surplus loop and a splice closure where the splice closurewill be located near the end of a cable reel: First insure that there isa sufficient length of cable on the end of the reel to make a completeforward loop beyond the pole (i.e., 25 feet ahead and 25 feet back) withthe end of the cable falling within five to six feet from the pole.

Since the invention is subject to modifications and variations, it isintended that the foregoing description and the accompanying drawingsshall be interpreted as only illustrative of the invention defined bythe following claims.

We claim:
 1. An apparatus for storing surplus ADSS cable having a specified minimum bend radius, said apparatus comprisinga pair of dead-ends for relieving cable tension at either end of a surplus loop of cable formed at a pole, so that the loop is substantially free of tension, a pair of bend radius protectors for maintaining at least the minimum bend radius at two bights formed in the loop when the center of the loop is raised to cable height, a pair of cable protecting sleeves, each mounted on the cable above the respective bend radius protectors, and means for suspending the bend radius protectors from the respective sleeves.
 2. The invention of claim 1, further comprising a cable guide mounted on the pole, said guide having channels for supporting the beginning of the loop, the end of the loop, and the middle of the loop.
 3. The invention of claim 2, wherein the cable guide comprises a base and means for attaching the base to the pole, and a cap and means for attaching the cap over the base, said channels being formed by mating grooves in the cap and base.
 4. The invention of claim 1, wherein the cable protection sleeve comprises an array of wires wound helically around the taut cable.
 5. The invention of claim 1, wherein the cable protection sleeve comprises a pair of mating half-shells installed on either side of the taught cable, and means for connecting the half shells to one another.
 6. The invention of claim 5, further comprising a bushing made of a plastic foam, within the sleeve, for gripping the cable surface to prevent the bend radius protector from swaying on the cable.
 7. The invention of claim 5, wherein the half-shells have tabs from which the bend radius protector can be suspended.
 8. The invention of claim 1, wherein the bend radius protector comprises a channel member formed in a teardrop shape, the channel member having a longitudinal groove for receiving the cable.
 9. The invention of claim 8, wherein one end of the teardrop shape has a radius at least ten times the diameter of the cable.
 10. The invention of claim 8, wherein one end of the teardrop shape has a radius no less than the minimum bend radius specified by the cable manufacturer.
 11. The invention of claim 8, wherein the channel member is reinforced by two cross-braces extending perpendicular to a plane of symmetry bisecting the teardrop shape.
 12. The invention of claim 11, further comprising means on each cross-brace for connection to the cable protection sleeve.
 13. The invention of claim 12, wherein the bend radius protector and the cable protection sleeve are made of a dielectric material.
 14. A fiber optic cable installation comprisinga series of poles installed in the ground and defining an aerial route at a specified cable installation height, a length of all-dielectric self-supporting cable supported by said poles at the installation height, a plurality of loops of surplus cable formed at intervals along said route, each loop being located at one of said poles, a pair of dead-ends defining the ends of each loop, said dead-ends being attached to the respective pole, means for supporting the center of the loop at the installation height on the pole, thus forming two bights of cable in the loop, a pair of bend radius protectors, one for each bight, and means for supporting the bend radius protectors from the taut cable, said means comprising a cable protecting sleeve installed over the taught cable above each said bend radius protector.
 15. A method of storing surplus ADSS cable having a specified minimum bend radius, the method comprising steps oflaying out a length of cable along an aerial route defined by a series of poles and forming loops of surplus cable at intervals, each said loop being at the location of one of said poles, raising the cable to a predetermined installation height at each of said poles, and securing the cable to the poles, at each loop location, affixing two dead-ends to the pole and securing the ends of the loop with the respective dead-ends so that the loop is substantially free of tension, raising the center of the loop to installation height and securing it to the pole while maintaining said minimum bend radius, thus forming two bights in the loop, installing a bend radius protector in each of the bights to protect the cable, installing a cable protecting sleeve over the main cable above each bend radius protector, and securing each bend radius protector only to a respective one of said sleeves. 